"This building will be studied in architecture books. It's a signpost of a hopeful future," says Jason Ballard shortly before tossing a ceremonial shovelful of dirt in Dallas to break ground on the second store for his Austin-based home improvement company, TreeHouse. "This will be the most sustainable and healthy building in Dallas, and perhaps the U.S."

Not exactly the words you expect to hear about a big box store being built on the site of a former Dave & Buster's, next to a busy freeway. But TreeHouse is no ordinary retailer, and Ballard is not an ordinary CEO.

The Dallas store, designed by the celebrated architecture firm Lake Flato, will look nothing like a giant windowless box. The plans call for a striking sawtooth-shaped roof, giant clerestory windows, enormous rooftop solar arrays, and a deep front porch. As "the world's first big box, net zero energy project," according to Lake Flato project director Lewis McNeel, the store will also function differently from any of its competitors--with its power bills literally reduced to nothing, thanks to a combination of sustainable energy and smart conservation strategies.

Co-founder Ballard, you might recall from our story about him last year, opened his first store in Austin with the intent to build a sort of Whole Foods for the DIY set, minus the rep for higher prices. The store, which offers eco-friendly home solutions such as rainwater barrels, solar panels, and toxin-free paints, has raised about $17 million from investors led by Container Store co-founder Garrett Boone (who is also TreeHouse's chairman) and captured the attention of some of the leading companies in the smart-home market. It was the first store anywhere to carry Tesla's Powerwall home battery, and reportedly sells more Nest devices than any other single store.

Whereas the typical home-improvement store is basically a giant shoppable warehouse, TreeHouse is more like an Apple store--an airy showroom with expert advisers on hand to help with project planning. When the original store opened almost five years ago, the company had no choice but to put it in a typical retail box in a large strip mall--albeit a nice one. That's worked well enough for the company to bring in about $10 million last year, and increase sales 40 percent this year. But Ballard knows all too well that his company's own physical presence hasn't had many of the environmentally-friendly features--nor the beautiful design--that he encourages for homeowners.

"One of the things about sustainable design is that it requires higher upfront investment and pays off over time with lower operating cost," he says. "We try all day long to convince people that's what they should do. And obviously, if we're not doing it ourselves, we're sending a message that it isn't worth it." The Dallas store is his chance to walk the walk. "This new building says to people, 'Hey, the financials make enough sense that even a business that has to be profitable can do this, even at a young startup phase where we don't have the flexibility and power of our competitors.'"

"The scale of this project pushed us way beyond what's been done before," says McNeel. "Big box retail is typically an extremely heavy energy user--a lot more than a home or other commercial buildings. The idea was, let's start with net zero energy and reverse engineer how to get there." As it turned out, one crucial design decision created a cascade of other opportunities, and the resulting design could establish a new template for many other businesses.

The Power of Triangles

A few days before the groundbreaking, Ballard shows me plans for the new building in his windowless, shared office behind the Austin store. "The twin strategies behind sustainable building are, first, to conserve as much energy as possible, and then to use renewable energy for whatever power needs you have left," he explains. The biggest energy hogs in a typical store are lighting and air conditioning, so the team set out to create something both bright and cool.

The key turned out to be that sawtooth roof line--a series of right triangles whose slopes face toward the front of the building with verticals toward the back. The verticals are giant clerestory windows that flood the interior space with natural light but, because they face north, no direct sunlight, which would bring in heat. The slopes of the triangles, set at the optimal angle for solar panels, face south, where they can collect the maximum amount of energy from the sun.

Finally, the slope of the first sawtooth extends out far beyond the storefront, creating a large, shaded front porch, which provides even more room for solar panels and allows for south-facing front windows that don't get direct sunlight. "So one design decision has three powerful impacts," Ballard says. It lights the space, reduces solar heat gain, and maximizes solar energy production. (Its fourth benefit--that it simply looks cool--was almost an afterthought, but it's probably what shoppers will most remember when they see it.)

During the day, Ballard says, the 25,000-square-foot building will be lit almost entirely by natural light (save for some spotlights around product displays). A Tesla battery will power the building in the evenings, using stored solar energy from the daytime. Further reducing cost, the interiors of the roof triangles create space for a mezzanine level, which means extra square footage for offices and meeting rooms without increasing the building's footprint.

Sawtooth roofs are nothing new, of course--they were common on factory buildings more than 100 years ago--but oddly enough, McNeel says, they haven't been used for this kind of large-scale sustainability trifecta until now.

Ballard estimates it will cost about 25 percent more to build the Dallas TreeHouse than it would to create a more traditional retail box. "At first, the developer [Dallas-based Cypress Equities] balked when we told them our plans. 'Lake Flato? Net zero energy? That roof?' But I said I'd pay for it as long as they let me realize the savings on my electric bill." He expects the savings to pay for the extra building cost in as little as seven years.

The Store That VR Built

TreeHouse's new store won't open until next April, but Ballard says he's already benefiting from one energy- and cost-saving innovation that arose from the design process. After he finished his second round of funding last summer, one of the first things he did was hire a team of designers and technologists--as opposed to, say, a CFO. And one of their first projects was to create a virtual-reality model of the new store, using a system they hacked together by combining the video game development platform Unity, the design program SketchUp, and an Oculus Rift headset.

That setup, which came together after they'd signed the Dallas lease and Lake Flato had begun its work, allowed them to walk through the new store to try different configurations and spot problems. An elaborate staircase to the mezzanine in the original design that was meant to evoke a tree trunk, for instance, turned out to be a hulking eyesore in VR, so they scrapped it for something simpler--and saved about $50,000 in the process.

Moving forward, as the company plans its third store (also in Texas, Ballard says, though he declines to specify where), he plans to use VR at every step--even in the site selection process. "If you're looking at real estate, before even considering the lease, you can get the rough measurements, throw the store together in VR, and realize, 'Hey, it's just not going to work here, because some element is going to be jarring.' VR is going to end up driving our real estate decisions."

He says he's already planning to create a full-time VR job for someone in the company. "I want to have a live model of all of our stores. If we have 50 stores, I want all 50 modeled, so as CEO I can drop in anywhere, try a few iterations of a display, and avoid costly trial-and-error changes. That will mean a lot less airplane travel, fewer fossil fuels burned, zero trees being cut down to produce displays that last six months because they were wrong. It's fast, cheap, and spot on for our mission of reducing our footprint."

In yet another trickle down effect, Ballard says virtual reality is going to become a core part of TreeHouse's project planning and consultation process with customers. "If we can figure out how to help design our customers' kitchens in VR, we will do it at every store, for free."

His real purpose, after all, is not to change how stores get built but how homes do. He's just questioning every assumption along the way.